PROJECT SUMMARY/ABSTRACT The Diabetes Prevention Program was a landmark randomized controlled trial that demonstrated the efficacy of a structured and comprehensive lifestyle intervention in preventing type 2 diabetes (T2D). Due to its large success, it was adapted for use in community settings by changing the intensive, individualized (one-on- one) lifestyle intervention to a facilitated, group-based intervention (Group Lifestyle Balance? [GLB]). While the GLB program has been associated with modest improvements in weight management and a reduced incidence of T2D in various community-based settings, reach has been limited. Healthcare system settings hold great potential for implementing behavioral lifestyle interventions due to the clinical resources and access to patients at risk for T2D. Natural experiments resulting from the spontaneous and organic implementation of evidence-based interventions, such as GLB, into a real-world clinical practice provide a rare and exciting opportunity to examine effectiveness in a truly pragmatic context. In the proposed study, Evaluation of a Lifestyle Intervention Adopted for Clinical Practice for Diabetes Prevention (ELEVATE-DP), we seek to evaluate the GLB program after its integration within a large, healthcare delivery system, Sutter Health (SH) of Northern California. SH is a mixed payer environment and operates as a fee-for-service organization, much like the U.S. healthcare system as a whole. In 2010, two of the five regional affiliates independently launched GLB programs. This allows for the unique opportunity to rigorously evaluate the real-world effectiveness of the GLB program after integration within a healthcare system, with high potential for the generalizability of findings to other similar health systems in the U.S. This study will employ a rigorous mixed-methods evaluation approach, using a large, comprehensive electronic health records (EHR) system, GLB program records, and prospectively collected primary data from past and present GLB administrators, facilitators, and participants, as well as eligible non-participants. We will use the EHR to retrospectively identify GLB participants (N=5,000) and a matched usual-care cohort (non-GLB participants; N=10,000) between 2010 and 2016, and will add four years of additional data (2017-2020). The Specific Aims are to: 1) Evaluate the clinical effectiveness of GLB relative to usual-care; 2) Evaluate the impact of GLB on healthcare resource utilization and costs relative to usual-care, including a formal cost-effectiveness analysis; and 3) Evaluate the implementation and fidelity of GLB within and across SH regional divisions and clinics using a comparative mixed-methods process evaluation. This study will identify important barriers to and facilitators of translating an efficacious diabetes prevention intervention into routine clinical practice, outside of a research setting.